In the never-ending arms race of American political fundraising, campaign receipts are up this year in every category but one: Republican presidential hopefuls.

GOP presidential primary contenders are thus far emerging as the big losers in an election that otherwise appears largely unaffected by the recession. As of the close of the third quarter, 13 GOP White House candidates had collected just shy of $90 million, public records show — about 40 percent less than the $150 million that 10 GOP primary contenders had raised at the same point in the 2008 cycle.

Several factors explain the downturn, political observers say, including the unpredictable and wide-open nature of the primary; the importance of closely watched debates instead of advertising in the campaign’s early stages; and the growing role of nonparty outside groups such as super political action committees.

If GOP White House candidates are the big losers, in fact, PACs appear to be the big winners in the chase for political dollars. PAC receipts totaled just more than $515 million as of the third quarter, according to the FEC, a jump of about 30 percent over the same point in the previous presidential election, when PACs had raised $394 million.

Boosting the PAC total are unrestricted super PACs, which have raised $54.3 million so far. Such PACs did not exist until last year’s Supreme Court ruling in Citizens United relaxed limits on campaign expenditures. Other groups that may be siphoning money from the candidates include nonprofits affiliated with the super PACs, which face no disclosure requirements and collect money under the radar, and 501(c)(6) trade associations that also face fewer restrictions in the wake of Citizens United.

Candidates “are competing with other types of entities,” said Jan Baran, an election lawyer with Wiley Rein. But Baran also sees other factors at play, including public frustration with politicians.

“There is just a decline in political enthusiasm across the board,” Baran said. “It’s the reason the president is getting negative poll numbers. It’s the reason Congress has historically low poll numbers. The public just doesn’t have a very high regard for politicians in general. If they’re unenthusiastic, they’re less likely to contribute.”

These trends have not dented President Barack Obama’s campaign coffers so far. He had raised $88.4 million by the close of the third quarter, FEC records show, compared with $78.8 million at the same point in 2007. But there’s evidence that Democrats are worried about the considerable sums being raised by GOP-friendly super PACs and nonprofits.

The Republican-run American Crossroads super PAC and its nonprofit affiliate, Crossroads GPS, for example, have doubled their combined fundraising target to $240 million for 2012. The Crossroads operation has spent more than $20 million so far. An Obama-friendly super PAC started by two White House aides known as Priorities USA Action, by contrast, has a $100 million target and has only spent about $1 million.

“We knew we’d be outspent, but we can keep up with them in terms of our message and being smart about where we target our efforts,” said one Priorities USA Action organizer. Still, this disparity has prompted top Democrats to convene strategy sessions and donor briefings aimed at closing the gap.

For the two major political parties, fundraising is a mixed bag so far. Both the Democratic and Republican party committees at the national and state level had raised more by the close of the third quarter than they had at the same point in 2007.

But fundraising has been uneven on both sides of the aisle. Assisted by Obama, the Democratic National Committee had pulled in $84.8 million by the close of the third quarter, a big jump over the $40.5 million that the DNC had collected at the same point in 2007. But fundraising at the Democratic committees backing House and Senate candidates was down slightly.

Republicans also raised more overall but lost ground at the Republican National Committee and at the state and local level, while the House and Senate GOP party committees reported increases at the third-quarter mark.

Whatever the cause, political advertising was way down in Iowa and New Hampshire as of early December. Combined advertising by campaigns and political groups in those two states totaled $3.7 million as of Dec. 6, according to a New York Times report citing data from Kantar Media’s Campaign Media Analysis Group. At the same point in 2007, political ads in those states was more than 10 times that amount, at $34.6 million.

“You’ve got to raise it before you can spend it,” said Ken Goldstein, president of CMAG. However, both states saw an ad surge by candidates and super PACs in late December. As the campaign accelerates, Goldstein predicted, campaign spending will once again break records, fueled in part by the super PACs that have now joined the ad wars.

“There has been less TV advertising,” Goldstein acknowledged, but he added: “That says nothing about what’s still going to be an enormous TV advertising air war in 2012.”